On the performance of large monolithic LaCl3(Ce) crystals coupled to pixelated silicon photosensors

TL;DR

This study evaluates large LaCl3(Ce) scintillation crystals coupled with pixelated silicon photosensors, demonstrating high energy resolution and analyzing the effects of sensor segmentation through experimental and Monte Carlo simulations.

Contribution

It provides the first detailed analysis of large monolithic LaCl3(Ce) crystals with pixelated SiPMs, including experimental measurements and Monte Carlo modeling of optical and segmentation effects.

Findings

Achieved 3.92% FWHM energy resolution at 662 keV

Validated Monte Carlo model with experimental data

Predicted minimal performance loss with pixel sizes up to 33 mm2

Abstract

We investigate the performance of large area radiation detectors, with high energy- and spatial-resolution, intended for the development of a Total Energy Detector with gamma-ray imaging capability, so-called i-TED. This new development aims for an enhancement in detection sensitivity in time-of-flight neutron capture measurements, versus the commonly used C6D6 liquid scintillation total-energy detectors. In this work, we study in detail the impact of the readout photosensor on the energy response of large area (5050 mm2) monolithic LaCl3(Ce) crystals, in particular when replacing a conventional mono-cathode photomultiplier tube by an 88 pixelated silicon photomultiplier. Using the largest commercially available monolithic SiPM array (25 cm2), with a pixel size of 66 mm2, we have measured an average energy resolution of 3.92% FWHM at 662 keV for crystal thicknesses of 10, 20 and 30 mm. The results are confronted with detailed Monte Carlo (MC) calculations, where both optical processes and properties have been included for the reliable tracking of the scintillation photons. After the experimental validation of the MC model, se use our MC code to explore the impact of different a photosensor segmentation (pixel size and granularity) on the energy resolution. Our optical MC simulations predict only a marginal deterioration of the spectroscopic performance for pixels of 33 mm2.